No wonder the Germans are so gung-ho on sending their diesels across the pond. Europe’s two-decade long diesel-keg party has been crashed by a new generation of super-efficient, clean and cheaper gasoline engines. A royal diesel-overproduction hang-over is inevitable. The Germans’ morning-after solution: send the stinky leftovers to enthusiastic Yanks waiting with open arms, who’ve conveniently forgotten their killer hangover from the last US diesel orgy.

In 1892, an experimental ammonia engine literally blew up in engineer Rudolph Diesel's face. Laid-up in a hospital bed, he pored over Nicolaus Otto’s pioneering work on the internal combustion engine. Diesel identified its weakness.

Diesel tumbled to the fact that the Otto engine’s efficiency was intrinsically compromised by the fact that it mixed fuel with air prior to compression. Too much compression resulted in uncontrolled pre-detonation. Diesel’s solution: inject fuel separately from the air to allow super-high compression and eliminating the need for a throttle (reducing pumping losses). Diesel's engine was roughly 30% more efficient than Otto's.

In 1989, VW/Audi ushered in the modern direct-injection (TDI) diesel. The group's oil burning powerplant set a high-water mark in the diesel’s long development. With Europe’s high fuel costs, the more expensive (yet efficient) diesel engine could now pay for itself quite easily. The calculation triggered Europe's diesel-boom, resulting in a 50 percent market share vs. gasoline-engined propulsion.

But Europeans have been paying a price (other than at the pumps): particulate emissions (Particulate Matter, or “PM”) and NOx pollution. Many European cities have serious particulate and diesel odor problems. Several European cities impose restrictions on diesels during PM alerts.

The new generation of “clean(er)” diesels that meet the US Tier2 bin5 standards cut PM emissions substantially, but not completely. Already, there are warnings that PM from “clean” diesels still poses a significant health risk.

The diesels coming our way carry several other penalties, especially versus the gasoline hybrid. The complicated and expensive NOx catalysts and urea injection schemes (“BlueTec”) cut efficiency by five percent. Meanwhile, the next Prius is projected to be 15 to 20 percent more efficient. And Toyota is bringing down hybrid production costs.

Then there's the elephant in the room: global warming. Clearly, the political winds are blowing against CO2. Diesel fuel has higher carbon content, resulting in 17 percent more CO2 per gallon of fuel burned than gasoline. With the diesel’s efficiency superiority down to 25 percent, a “clean” diesel emits only 13 percent less CO2 than yesterday’s gas engine. And that small gap is… wait… gone.

While the diesel’s efficiency peaked in 1989, and lost 5 percent to PM cleansing, gas engine development is on a roll. Engineers are systematically tackling all the inherent deficiencies that Diesel identified in his hospital bed. (No wonder Rudolf was considered paranoid; maybe he suspected that eventually the Otto engine would catch up.)

A farrago of new gas-engine technologies has converged, which Europeans have been quick to embrace. VW’s 1.4-liter 170hp TSI gas engine is a perfect example of the trend. The TSI starts off with the help of a supercharger (no turbo-lag), and then switches to turbocharging (no parasitic losses). With diesel-like torque and direct injection, it’s the best of both worlds.

American Rabbit drivers are paying a whopping 38 percent efficiency penalty compared to the Euro-Golf TSI, as well as giving up gobs of torque and twenty horsepower. If VW’s 170hp TDI were “cleansed” to T2b5 standards, its CO2 output would be no better then the gasoline TSI.

And that’s just the jumping-off point. Start-stop technology, full valve control, and stratified direct-injection offer anywhere from 10 to 25 percent further improvement potential. Combine these goodies with mild-hybrid assist/regeneration, and the diesel party’s kaput. No wonder the Germans are all hard at work on mild-hybrid technology. It’s their best shot to keep up with Toyota’s CO2 meister, the Prius (102g/km).

A study by the consulting firm AT Kearny confirms the diesel's demise. It predicts that only 25 percent of Europeans will find diesels an attractive economic proposition by 2020.

Have Rudolf Diesel’s paranoid nightmares come true? Not totally. Diesels are a welcome mix to the party for larger vehicles that spend a lot of time on the open road. Count on GM’s new 4.5-liter “baby” Duramax diesel to be more popular with the light-truck crowd than the gas hybrid option. But when it comes to smaller vehicles, the numbers just don’t add up.

Although Rudolf Diesel’s engine WAS intrinsically more efficient, it turns out that Otto’s engine is a lot more clever at learning new tricks.

This week's cover story, 'The truth about diesel', is the result of more than 12 months of research.

We've suspected for some time diesel isn't the saviour of the world's environmental problems that it has been made out to be. And, indeed, this is the view of the many experts we've interviewed who've become frustrated by the recent hype about diesel.

Sales of diesel cars have increased by a staggering 139 per cent in the first four months of 2007 compared with the same period last year. Indeed, Australians have already bought more diesel cars in the past four months than they did in all of 2005.

We have questioned the financial benefit of diesel cars for some time. If you calculate the $3000-plus price premium compared with a petrol car and then figure out the savings in fuel economy, it will take about nine years to reap the cost benefits based on the average distance travelled by Australian motorists.

Now there is good reason to be worried about the health implications of diesel. To be blunt, diesel emissions can give you cancer. Research Drive has unearthed shows diesel is responsible for more deaths each year than the road toll - and yet governments appear to be giving the diesel problem far less attention. Perhaps that's because there's no revenue in it.

Apparently the NSW State Government is reluctant to introduce emissions checks on cars at registration renewal time because it is concerned about the impact it would have on low-wage earners. Yet the same government happily imposes the most expensive traffic fines and stiffest penalties in Australia.

The Federal Government, too, is far from blameless on this issue. The quality of diesel fuel in Australia lags well behind more stringent regulations in Europe and other countries. If a car maker's new model doesn't meet the latest emissions requirements, it isn't allowed to be sold in Australia. When petrol companies stretch a deadline, there appears to be no punishment.

Diesel has a place, especially in heavy transport, and technology is slowly making it cleaner. But even when more restrictions are in place in 2009, diesel will still not be as clean as unleaded petrol. Cigarette packets carry warning labels. Where are the warnings on diesel vehicles?

The truth about diesel - Diesel produces fewer greenhouse gases than unleaded petrol but it is more dangerous to our health. RICHARD BLACKBURN reports on an automotive dilemma.

Richard Blackburn, The Sydney Morning Herald, 01/06/07

Demand for diesel-powered cars is soaring. Australians bought more diesel cars in the first four months of this year than they did in the whole of 2005.

Sales this year are up 135 per cent on the same period last year and the latest figures show that almost 20 per cent of new vehicles sold this year are powered by diesel. In 2000, the figure was just 10 per cent.

However, the explosive growth is a double-edged sword.

The good news is that diesel-powered engines are more efficient than their petrol cousins and therefore emit less CO2 - the major contributor to global warming.

The bad news is that emissions from diesel engines are harmful to your health. That includes the latest generation of so-called "clean" diesels.

The Federal Government's Green Vehicle Guide, which ranks vehicles on their greenhouse gas and air pollution performance, doesn't have a single diesel vehicle in its top 50 list of low polluters.

Just one makes the top 150 and there are only five in the top 200 vehicles.

Jon Real, a spokesman for the Federal Department of Transport, which maintains the guide, says diesel cars are marked down because they have a "much more significant health effect".

He says diesels produce about the same amount of hydrocarbons as petrol but significantly more nitrogen oxides (NOx) - a precursor to smog - and particulate matter.

Air quality experts estimate that diesel engines produce particles at about 20 times the rate of petrol engines and it is those emissions that are bad for your health.

Particulate matter has been linked with thousands of deaths worldwide. Side effects range from cancer to respiratory and cardiovascular diseases. NOx have also been linked to serious health problems, including asthma, respiratory disease, infections and reduced lung function in children.

A recent NSW parliamentary inquiry into air quality found that motor vehicles produce 71 per cent of NOx emissions in Sydney and just under 20 per cent of particle pollution.

Real says particulate matter emissions carry a hefty weighting in the department's assessment of pollution effects from different vehicles. It's easy to see why.

The most recent figures from the Bureau of Transport and Regional Economics - for 2000 - put the annual death toll from vehicle exhaust pollution at between 900 and 2000 people - higher than the national road toll. It is also estimated to contribute to between 700 and 2050 asthma attacks in Australia each year.

Diesel fumes are accepted as the major contributor to these figures. "Diesel exhaust has been linked in numerous scientific studies to cancer, the exacerbation of asthma and other respiratory diseases," the bureau's report says.

The Chairman of the Lane Cove Tunnel Action Group and immunologist, associate professor Ray Kearney, says vehicle exhaust has been reported to stunt lung development in children. Kearney says Australian authorities have been slow to legislate against harmful pollutants produced by motor vehicles.